Method and apparatus for establishing non-standard data rates in a wireless communication system

0001This patent application is claiming priority under 35 USC § 120 as a continuing patent application of patent application entitled METHOD AND APPARATUS FOR ESTABLISHING NON-STANDARD DATA RATES IN A WIRELESS COMMUNICATION SYSTEM, having a filing date of Dec. 18, 2001, and a Ser. No. 10/026,129 now U.S. Pat. No. 7,099,398.

TECHNICAL FIELD OF THE INVENTION

0002This invention relates generally to wireless communication systems and more particularly to varying data rates of transmissions within such a wireless communication system.

BACKGROUND OF THE INVENTION

0003Wireless communication systems are known to include a plurality of wireless communication devices that communicate directly (e.g., point-to-point) or through an infrastructure. For direct communications, a wireless communication device, such as a radio, cellular telephone, station coupled to a personal computer or laptop, et cetera, transmits data on a particular radio frequency channel directly to another wireless communication device. For infrastructure-supported communications, a wireless communication device transmits data on an assigned radio frequency channel to an access point (or a base station). The access point determines the targeted wireless communication device from the received RF signals. If the targeted wireless communication device is affiliated with the access point, the access point transmits the data to the targeted wireless communication device on a radio frequency channel. If the targeted wireless communication device is not affiliated with the access point, the access point forwards the data to a central station, which routes the data to the access point that is affiliated with the targeted wireless communication device.

0004To ensure reliability of data transmissions within a wireless communication system and to ensure interoperability of differing manufacturers' equipment, standards have been developed. Such wireless communications standards include IEEE8 02.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), wireless application protocols (WAP), local multi-point distribution services (LMDS), multi-channel, multi-point distribution systems (MMDS), and/or variations thereof.

0005Such standards prescribe operating parameters for a particular type of wireless communication system. For example, the IEEE 802.11a standard defines a wireless local area network that prescribes a frequency band of use, division of the frequency band into channels and sub-channels, encoding/decoding convention, modulation/demodulation convention, frame format, data rates, et cetera. For instance, the IEEE 802.11a standard provides various combinations of data rates and modulation schemes, which can be selected via a coding rate corresponding to a particular modulation scheme.

0006As is known for wireless local area networks, wireless communications devices roam within the coverage area of the wireless local area network. As such, signal strength of radio frequency signals to and from a wireless communication device varies depending on the interference between the wireless communication device and another wireless communication device or the access point and the distance therebetween. In accordance with the IEEE 802.11a standard, data rates and modulation schemes may be adjusted based on signal strength and/or interference of RF signals. For example, if the signal strength is strong and there is minimal interference, the communication may be done at 54 Mbps (megabits per second) using a 64 QAM (quadrature amplitude modulation) modulation scheme. If, on the other hand, the signal strength is weak and/or there exists substantial interference, the communication may be done at 6 Mbps using a BPSK (binary phase shift keying) modulation scheme.

0007The various combinations of data rates and modulation schemes prescribed by the IEEE 802.11a standard provides adequate granularity of data rates for typical data transmissions (e.g., email, file transfers, and internet access) for wireless communication devices that move within the local area network. However, for relatively stationary wireless communication devices that transmit and/or receive video data, the granularity of data rates provided by the IEEE 802.11a standard may not be sufficient. For example, the IEEE 802.11a standard provides a 24, 36 and 48 Mbps data rates, which are spaced at 12 Mbps. Thus, if a wireless communication device barely fails to support a 48 Mbps rate it drops to a 36 Mbps data rate. For MPEG video streams, which have a bandwidth of about 2 Mbps, the change from 48 Mbps to 36 Mbps reduces the number of video streams that a channel can support by 6. Such a loss of potential video streams on a particular channel in many applications is highly undesirable.

0008Therefore, a need exists for a method and apparatus that provides for greater granularity of standardized data rates in a standard compliant wireless communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

0009<figref idref="DRAWINGS">FIG. 1</figref> illustrates a schematic block diagram of a transmitter section of a wireless communication device in accordance with the present invention;

0010<figref idref="DRAWINGS">FIG. 2</figref> illustrates a receiver section of a wireless communication device in accordance with the present invention;

0011<figref idref="DRAWINGS">FIG. 3</figref> illustrates a logic diagram of a method for establishing non-standard data rates in accordance with the present invention;

0012<figref idref="DRAWINGS">FIG. 4</figref> illustrates a logic diagram that further describes Step <b>70</b> of <figref idref="DRAWINGS">FIG. 3</figref>;

0013<figref idref="DRAWINGS">FIG. 5</figref> illustrates a graphical diagram of error thresholds in accordance with the present invention; and

0014<figref idref="DRAWINGS">FIG. 6</figref> illustrates a logic diagram that further describes Step <b>72</b> of <figref idref="DRAWINGS">FIG. 3</figref>.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

0015Generally, the present invention provides a method and apparatus for establishing a non-standard data rate in a wireless communication system. Such a method and apparatus include processing that begins by establishing a standard specified data rate for a given transmission (e.g., selecting a data rate in accordance with a standard). The processing then continues by determining whether the data rate of the transmission can be adjusted from the standard specified data rate by a non-standard data rate adjustment (e.g., error rate is sufficient to support a data rate greater than the selected data rate, but may not be sufficient to support next higher standardized data rate). The processing then continues when the data rate can be adjusted, adjusting the data rate to a non-standard data rate for the given data transmission. With such a method and apparatus, finer granularity of data rates is achieved, thus allowing local area networks to support additional streams of data on a given channel, including MPEG video data, in comparison to local area networks that only use the standardized data rates.

0016The present invention can be more fully described with reference to <figref idref="DRAWINGS">FIGS. 1 through 6</figref>. <figref idref="DRAWINGS">FIG. 1</figref> illustrates a schematic block diagram of a transmitter section of a wireless communication device <b>10</b>. The wireless communication device <b>10</b> includes an encoding module <b>12</b>, a puncture module <b>14</b>, a modulation mapping module <b>16</b>, a transmission section <b>36</b>, and a rate determining module <b>18</b>. The rate determining module <b>18</b> includes a processing module <b>32</b> and memory <b>34</b>. As one of average skill in the art will appreciate, the encoding module <b>12</b>, the puncture module <b>14</b>, and the mapping module <b>16</b> may be implemented as separate components, within a common processor, and/or within the processing module <b>32</b> and memory <b>34</b>.

0017The processing module <b>32</b> may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, and/or any device that manipulates signals (analog and/or digital) based on operational instructions. The memory <b>34</b> may be a single memory device or a plurality of memory devices. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that stores digital information. Note that when the processing module <b>32</b> implements one or more of its functions via a state machine or logic circuitry, the memory storing the corresponding operational instructions is embedded with the circuitry comprising the state machine or logic circuitry. The memory <b>34</b> stores, and the processing module <b>32</b> executes, operational instructions corresponding to at least some of the steps illustrated in <figref idref="DRAWINGS">FIGS. 3</figref>, <b>4</b>, and <b>6</b>.

0018The encoding module <b>12</b> is operably coupled to receive data <b>20</b> and produce therefrom encoded data <b>22</b>. For an IEEE 802.11a compliant wireless communication device, the encoding module <b>12</b> performs a convolution encoding that produces two outputs, A and B. In addition, the encoding module <b>12</b> may interleave the encoded data bits in a block size that corresponds to the number of bits in a single orthogonal frequency division multiple (OFDM) symbol.

0019The puncture module <b>14</b> receives the encoded data and increases the data rate to produce punctured data <b>24</b>. For an IEEE 802.11a compliant device, the puncture module <b>14</b> omits some of the encoded bits in the transmitter such that the receiver inserts a dummy “zero” metric into the convolution decoder in place of the omitted bits. The particular level at which the rate is increased corresponds to the coding rate <b>28</b> provided by the rate determining module <b>18</b>.

0020The modulation mapping module <b>16</b> receives the punctured data <b>24</b> and maps it to produce the modulated data <b>26</b>. For an IEEE 802.11a compliant device, the modulation mapping module <b>16</b> maps the punctured data <b>24</b> based on a particular modulation mode <b>30</b>. For IEEE 802.11a, the modulation modes include BPSK, QPSK (quadrature phase shift keying), 16 QAM, or 64 QAM. The transmission section <b>36</b> receives the modulated data <b>26</b>, up-converts it to an RF frequency, and transmits it as an RF signal <b>38</b>.

0021The rate determining module <b>18</b>, performs at least some of the operations illustrated in <figref idref="DRAWINGS">FIGS. 3 through 6</figref> to determine a particular coding rate <b>28</b> and modulation mode <b>30</b>. In general, the rate determining module <b>18</b>, within memory <b>34</b>, stores the standard data rates <b>35</b>. For an IEEE 802.11a, the standard data rates are as shown in <figref idref="DRAWINGS">FIG. 1</figref>. In addition, the rate determining module <b>18</b> determines whether the wireless communication device <b>10</b> can support non-standard data rates. Such a determination is made based on signal strength and/or interference levels. For example, assume that the rate determining module <b>18</b> determines that the wireless communication device <b>10</b> could not support a data rate of 24 Mbps but could support a rate of 18 Mbps. Having made this determination, the rate determining module <b>18</b> determines an error rate and corresponding error margin of the selected standardized data rate (e.g., 18 Mbps) based on one or more factors including received signal strength indication, bit error rate, acknowledgment back of transmitted signals, signal-to-noise ratio, signal-to-interference ratio, packet error rate, bit error rate, et cetera. If a sufficient error margin exists, the rate determining module <b>18</b> determines a non-standard data rate and a corresponding modulation scheme from a non-standard data rate table <b>37</b>. For this example, the rate determining module <b>18</b> selects the non-standard data rate of 21 Mbps and a QPSK modulation mode <b>30</b>. The rate determining module <b>18</b> indicates to the puncture module <b>14</b> and the modulation mapping module <b>16</b> the selected non-standard data rate and corresponding modulation mode through the coding rate signal <b>28</b> (e.g., which is set to 7/8) and the modulation mode signal <b>30</b>, respectively.

0022The rate determining module <b>18</b> may also determine non-standard data rates that lie between the standard rates of 12 and 18 Mbps, between 24 and 36 Mbps, between 36 and 48 Mbps, between 48 and 54 Mbps and above 54 Mbps as shown in <figref idref="DRAWINGS">FIG. 1</figref>. In addition to changing the data rates to non-standard data rates, for example, 15, 21, 30, 42, 62 or 66 megabits-per-second, the rate determining module <b>18</b> may also use a non-standard modulation technique.

0023<figref idref="DRAWINGS">FIG. 2</figref> illustrates a receiving section of a wireless communication device <b>40</b>. The wireless communication device <b>40</b> includes a receiver section <b>42</b>, demodulation mapping module <b>44</b>, depuncture module <b>46</b>, decoding module <b>48</b> and a rate determining module <b>50</b>. The rate determining module <b>50</b> includes a processing module <b>52</b> and memory <b>54</b>. As one of average skill in the art will appreciate, the demodulation mapping module <b>44</b>, depuncture module <b>46</b>, and the decoding module <b>48</b> may be implemented as separate components, within a common processor, and/or within the processing module <b>52</b> and memory <b>54</b>.

0024The processing module <b>52</b> may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, and/or any device that manipulates signals (analog and/or digital) based on operational instructions. The memory <b>54</b> may be a single memory device or a plurality of memory devices. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that stores digital information. Note that when the processing module <b>52</b> implements one or more of its functions via a state machine or logic circuitry, the memory storing the corresponding operational instructions is embedded with the circuitry comprising the state machine or logic circuitry. The memory <b>54</b> stores, and the processing module <b>52</b> executes, operational instructions corresponding to at least some of the steps illustrated in <figref idref="DRAWINGS">FIGS. 3</figref>, <b>4</b>, and <b>6</b>.

0025The rate determining module <b>50</b> includes the standard data rates <b>35</b> and non-standard data rates <b>37</b> as illustrated in <figref idref="DRAWINGS">FIG. 1</figref>. In operation, the receiving section <b>42</b> receives an RF signal <b>56</b>, down-converts the RF signal <b>56</b> to a base-band signal, and filters it to produce a digital signal <b>58</b>. The demodulation mapping module <b>44</b> demodulates the digital signal <b>58</b> to produce demodulated data <b>60</b>. The rate determining module <b>50</b> interprets the digital signal <b>58</b> to determine the particular coding rate <b>28</b> and modulation mode <b>30</b> used to encode the data conveyed by the RF signal <b>56</b>. Once determined, the rate determining module <b>50</b> generates the modulation mode <b>30</b> and coding rate <b>28</b>, which are provided to the demodulation mapping module <b>44</b> and the depuncture module <b>46</b>, respectively.

0026Having received the modulation mode signal <b>30</b>, the demodulation mapping module <b>44</b> demodulates the digital signal <b>58</b> accordingly to produce demodulated data <b>60</b>. The depuncture module <b>46</b> subsequently depunctures (i.e., reduces the data rate) the demodulated data <b>60</b>, based on the coding rate <b>28</b>, to produce depunctured data <b>62</b>. Next, the decoding module <b>48</b> decodes the depunctured data <b>62</b> to produce decoded data <b>64</b>.

0027As one of average skill in the art will appreciate, if the wireless communication device includes both a transmitter section and receiver section, processing module <b>32</b> and processing module <b>52</b> may be the same processing module. Similarly, memory <b>34</b> and memory <b>54</b> may be the same memory. As one average skill in the art will further appreciate, the processing module and memory may be utilized to implement the encoding module <b>12</b>, puncture module <b>14</b> and/or mapping module <b>16</b>. In addition, the processing module and memory may be used to implement the demodulation mapping module <b>44</b>, depuncture module <b>46</b> and/or decoding module <b>48</b>.

0028<figref idref="DRAWINGS">FIG. 3</figref> illustrates a logic diagram of a method for establishing a non-standard data rate in a wireless communication system. The processing begins at Step <b>70</b> where a standard specified data rate is established for a given transmission. In one embodiment, this may be done by selecting a standard rate of a plurality of standard data rates from a table. For example, the standard data rate may default to the minimal data rate of 6 megabits-per-second using BPSK modulation. As one of average skill in the art will appreciate, any of the standard data rates and corresponding modulation schemes may be used to establish the particular data rate for Step <b>70</b>.

0029The process then proceeds to Step <b>72</b> where a determination is made as to whether the data rate of the given transmission can be adjusted to a non-standard data rate. The details of the determination will be described in greater detail with reference to <figref idref="DRAWINGS">FIG. 6</figref>. If not, the process proceeds to Step <b>74</b> where the standard specified data rate is used for the given transmission.

0030If, however, the rate can be adjusted, the process proceeds to Step <b>76</b>. At Step <b>76</b>, the standard specified data rate is adjusted by a non-standard data rate adjustment to produce a non-standard data rate for the given transmission. To change to the non-standard data rate, the coding rate is changed to correspond to a non-standard coding rate. Alternatively, and/or in addition to, the non-standard data rate adjustment may correspond to selecting a different constellation encoding, which corresponds to a non-standard constellation encoding scheme.

0031The process then proceeds to Step <b>78</b> where a message is sent to indicate the non-standard data rate to a wireless communication device that is targeted to receive the data transmission. Note that the message may be sent in the normal course of transmission utilizing the training sequence to establish the non-standard data rate.

0032<figref idref="DRAWINGS">FIG. 4</figref> illustrates a logic diagram that illustrates an alternate embodiment for establishing the standard specified data rate. This may be done during the training period of a frame or plurality of frames for the given transmission. The process begins at Step <b>80</b> where a 1^ststandard data rate of the plurality of data rates is selected for the given transmission. This may be done by making an arbitrary selection from the standard data rates or based on a histogram of previously used standard data rates. Such a histogram may be based on a single previously used standard data rate or a plurality of previously used standard data rates.

0033The process then proceeds to Step <b>82</b> where a determination is made as to whether the selected standard data rate provides an acceptable error rate. The determination of the acceptable error rate will be graphically described with reference to <figref idref="DRAWINGS">FIG. 5</figref> below.

0034If the selected data rate does not provide an acceptable error rate, the process proceeds to Step <b>84</b> where another standard data rate of the plurality of standard data rates is selected. Having done this, the process repeats at Step <b>82</b>. If, however, the selected standard data rate provides an acceptable error rate, the process proceeds to Step <b>86</b>. At Step <b>86</b>, the selected standard data rate is used as the standard specified data rate.

0035<figref idref="DRAWINGS">FIG. 5</figref> illustrates the mapping of a QPSK modulation scheme. As shown, the 2-bit representation is symbolically represented by the quadrant in which the data point is received. In actual data transmissions, the received symbols will fall in one of the four quadrants forming a scatter pattern around the ideal location (the ideal location is illustrated in <figref idref="DRAWINGS">FIG. 5</figref>). If the scatter pattern is widely concentrated, i.e., indicating that the signal power to noise power ratio is below the lower error threshold <b>88</b>, the error rate is too great thus indicating a non-acceptable error rate. As such, the data rate would need to be decreased for this particular example. If on the other hand, the scatter pattern is narrowly concentrated with respect to the upper error threshold <b>90</b>, this would indicate that signal power to noise power ratio is high, thus allowing the data rate to be increased. As one of average skill in the art will appreciate, the error may be interpreted utilizing one or more of received signal strength indication, bit error rate, percentage of acknowledgments of data transmissions, signal-to-noise ratio, packet error rate, signal-to-interference ratio, and/or bit error rate.

0036<figref idref="DRAWINGS">FIG. 6</figref> illustrates a logic diagram that provides an embodiment for determining whether the data rate can be adjusted to a non-standard data rate. The process begins at Step <b>92</b> where an error indication is interpreted with respect to the lower error threshold and/or the upper error threshold. This is done by comparing the signal power to noise power ratio with the lower error threshold <b>88</b> and the upper error threshold <b>90</b> to provide the error indication.

0037The process then proceeds to Step <b>94</b> where an error margin is determined between the error indication and the upper and lower thresholds. Referring back to <figref idref="DRAWINGS">FIG. 5</figref>, the error margin indicates the difference between the circumference of the error scatter pattern and the lower error threshold <b>88</b> and the upper error threshold <b>90</b>, i.e., the difference between the actual signal power to noise power ratio and the ratio for the upper and lower thresholds <b>88</b> and <b>90</b>. For example, if the scatter pattern circumference is close to the lower error threshold <b>88</b>, there is a small error margin. If, however, the scatter pattern is close to the upper error threshold <b>90</b>, there is a larger error margin.

0038The process then proceeds to Step <b>96</b> where the non-standard data rate adjustment is determined based on the error margin. The determination of the non-standard data rate may be done by incrementally adjusting the data rate to non-standard data rates. Having made the adjustment, the error margin is determined for the newly adjusted non-standard data rate. If the error margin is small, i.e., the scatter pattern is close to the lower error threshold <b>88</b>, that particular non-standard data rate is used. If, however, there is still sufficient error margin, the data rate is incremented to the next non-standard data rate level and the error margin is determined for this level. In practice, one would want the scatter pattern for the non-standard data rate to lie substantially near the lower error threshold <b>88</b>, thus maximizing the bandwidth of a given channel.

0039With such a method and apparatus, non-standard data rates may be utilized within a standard compliant wireless communication system to provide finer granularity of channel use. Such finer granularity is particularly useful in local area networks that transmit video data. Accordingly, by providing finer granularity in data rates, additional video streams may be transmitted thereby increasing the capabilities of a local area network. As one of average skill in the art will appreciate, other embodiments may be derived from the teachings of the present invention without deviating from the scope of the claims.